Methods and systems to facilitate operating within flame-holding margin

ABSTRACT

A method to facilitate controlling flame-holding margins in a turbine engine is provided. The method includes coupling at least one turbine nozzle segment within the turbine engine, wherein the at least one turbine nozzle segment includes at least one vane extending between an inner band and an outer band. The method also includes positioning at least one fuel injection orifice in a surface of the at least one vane, channeling a fuel through the at least one fuel injection orifice into a compressed fluid flow to establish a jet penetration height, and defining an operating window by adjusting an operating parameter of the fuel to reduce the jet penetration height and to facilitate reducing the flame-holding margins.

BACKGROUND OF THE INVENTION

This invention relates generally to turbine assemblies, and moreparticularly, to methods and systems to facilitate controllingflame-holding margins during turbine operation.

Generally, turbine assemblies used in power generation systems aredesigned for use with a particular fuel. More specifically, knownturbines are designed to achieve mandated nitrous oxide (NOx) emissionlevels when operating. However, as the cost of gaseous fuels hasincreased, while gas fuel supplies have become more difficult to secure,at least some known turbines have had to operate with alternative fuels.

At least some known methods of operating turbine assemblies economizefuel consumption by increasing the temperature of the fuel supplied tothe turbines using waste heat. By increasing the temperature of the fuelsupplied to the turbine, less energy is required to bring the fuel to aturbine operating temperature. For example, in a turbine having anoperating temperature of 2500° F., fuel having an initial temperature of100⁰ F is heated to between about 300 to 400° F. using waste heat, andthen additional energy is required to heat the fuel to the 2,500° F.operating temperature. Thus, pre-heating the fuel using waste heatfacilitates decreasing the quantity of energy necessary to reach anexhaust temperature that produces a corresponding desired amount ofpower.

Using these methods with non-design gas fuels may decrease the fuelnozzle's flame-holding margins below the desired allowable limits. Flameholding may damage the fuel nozzle, creating hot streaks that exceed thelocal maximum operating temperature of turbine engines, thus causingturbines to fail. Moreover, exceeding flame-holding margins may alsolimit the useful life of the fuel nozzles and/or may cause damage to thecombustor lining.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a method to facilitate operating within flame-holdingmargins in a turbine engine is provided. The method includes coupling atleast one turbine nozzle segment within the turbine engine, wherein theat least one turbine nozzle segment includes at least one vane extendingbetween an inner band and an outer band. The method also includespositioning at least one fuel injection orifice in a surface of the atleast one vane, channeling a fuel through the at least one fuelinjection orifice into a compressed fluid flow to establish a jetpenetration height, and defining an operating window by adjusting anoperating parameter of the fuel to reduce the jet penetration height andto facilitate increasing the flame-holding margins.

In another exemplary embodiment, a system to facilitate operating withinflame-holding margins in a turbine engine is provided. The systemincludes at least one turbine nozzle segment coupled within the turbineengine, where the at least one turbine nozzle segment includes at leastone vane extending between an inner band and an outer band. The systemalso includes a design fuel from a fuel source, at least one fuelinjection orifice defined in a surface of the at least one vane, wherethe at least one fuel injection orifice is designed to optimize turbineperformance using the design fuel. A non-design fuel is channeledthrough the at least one fuel injection orifice into a compressed fluidflow to establish a jet penetration height, and an operating windowfacilitates reducing the jet penetration height and facilitatesincreasing the flame-holding margins.

In yet another exemplary embodiment, a turbine engine is disclosed. Theturbine engine includes a nozzle assembly including an inner band, anouter band, and at least one vane extending between the inner band andthe outer band. The vane includes a plurality of fuel injection orificesdesigned to optimize performance using a design fuel and are configuredto channel a non-design fuel therefrom to facilitate controllingflame-holding margins.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective cross-sectional view of an exemplary turbinenozzle assembly;

FIG. 2 is an enlarged perspective view of a swirler assembly used in theturbine nozzle assembly shown in FIG. 1;

FIG. 3 is an enlarged perspective view of a portion of the swirlerassembly shown in FIG. 2;

FIG. 4 is an enlarged cross-sectional view of an exemplary fuel jet andflame-holding margin;

FIG. 5 is a schematic diagram of an exemplary operating window foroperating a nozzle assembly with a non-design gas fuel; and

FIG. 6 is a schematic diagram of an alternate operating window foroperating a nozzle assembly with the same non-design gas fuel used inFIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a cross-sectional view of an exemplary nozzle assembly 10. Inthe exemplary embodiment, nozzle assembly 10 is divided into fourregions by function including an inlet flow conditioner (IFC) 12, aswirler assembly 14 with fuel injection, an annular fuel fluid mixingpassage 16, and a central diffusion flame fuel nozzle assembly 18.Nozzle assembly 10 also includes a high pressure plenum 20 having aninlet end 22 and a discharge end 24. High pressure plenum 20circumscribes nozzle assembly 10. Discharge end 24 does not circumscribenozzle assembly 10, but rather discharge end 24 extends into a combustorreaction zone 26. IFC 12 includes an annular flow passage 28 that isdefined by a solid cylindrical wall 30. Wall 30 defines an insidediameter 32 for passage 28, and a perforated cylindrical outer wall 34defines an outside diameter 36. A perforated end cap 38 is coupled to anupstream end 40 of nozzle assembly 10. In the exemplary embodiment, flowpassage 28 includes one or more annular turning vanes 42. Duringoperation, compressed fluid enters IFC 12 via perforations in end cap 38and cylindrical outer wall 30. Moreover, it should be understood that inthe exemplary embodiment nozzle assembly 10 defines a premix gas fuelcircuit that enables design gas fuel and compressed fluid to be mixedprior to combustion.

As used herein the term “design gas fuel” is the particular gas fueloriginally selected to enable a corresponding turbine engine to achievea demand power output by design. Non-design gas fuels may also be usedto power turbine engines and are different from design gas fuels. In theexemplary embodiment, the design gas fuel is a methane-based gas.However, it should be appreciated that in other embodiments the designgas fuel may be any gas fuel that facilitates powering a turbine engineas described herein. In the exemplary embodiment, non-design gas fuelsinclude no-methane based gas fuels, such as, but not limited to,liquefied natural gas (LGN), non-design gas fuels and process gas fuels.

FIG. 2 is an enlarged perspective view of an exemplary swirler assembly14 that may be used with nozzle assembly 10 (shown in FIG. 1). FIG. 3 isan enlarged perspective view of a portion of swirler assembly 14.Swirler assembly 14 includes a plurality of vanes 44 that each extendbetween a radially outer band 46, having an outer surface 48, and aradially inner band 50, having an outer surface 52. Each vane 44includes a suction sidewall 54 and a pressure sidewall 56. Suctionsidewall 54 is convex and defines a suction side of vane 44, andpressure sidewall 56 is concave and defines a pressure side of vane 44.Sidewalls 54 and 56 are joined at a leading edge 58 and at anaxially-spaced trailing edge 60 of vanes 44.

Suction and pressure sidewalls 54 and 56, respectively, extendlongitudinally, in span between radially inner band 50 and radiallyouter band 46. A vane root 62 is defined as being adjacent inner band50, and a vane tip 64 is defined as being adjacent outer band 46.

It should be understood that turning vanes 44 impart swirl to compressedfluid passing through swirler assembly 14. Moreover, turning vanes 44each include a primary fuel supply passage 66 and a secondary fuelsupply passage 68 defined in a core (not shown) of each vane 44. In theexemplary embodiment, each vane pressure side 56 includes a plurality ofgas fuel injection orifices 70 and a plurality of secondary gas fuelinjection orifices 72. In the exemplary embodiment, orifices 70 and 72each have a substantially circular shape, and orifices 70 have a largercross-sectional area than orifices 72. It should be understood thatprimary injection orifices 70 and secondary injection orifices 72penetrate pressure sidewall 56 of each vane 44. Moreover, it should beappreciated that in other embodiments, fuel injection orifices 70 and 72may be located on vane suction side 54, or on both pressure and suctionsides 56 and 54, respectively. Furthermore, although orifices 70 and 72are described as having a substantially circular shape, in otherembodiments, orifices 70 and 72 may have any shape, orientation, orconfiguration that enables nozzle assembly 10 to function as describedherein.

During operation, primary fuel passage 66 and secondary fuel passage 68distribute gas fuel to primary injection orifices 70 and secondaryinjection orifices 72, respectively. Gas fuel enters swirler assembly 14through inlet port 74 (shown in FIG. 1) and annular premix gas fuelpassages 76 and 78 (shown in FIG. 1). Annular premix gas fuel passages76 and 78 supply primary 66 and secondary 68 fuel supply passages,respectively. The gas fuel mixes with compressed fluid in swirlerassembly 14, and fuel/air mixing is completed in annular premix passage16 (shown in FIG. 1). Passage 16 is defined by a nozzle hub extension 80(shown in FIG. 1) and a nozzle shroud extension 82 (shown in FIG. 1). Itshould be appreciated that most of the compressed fluid for combustionenters nozzle assembly 10 via IFC 12, and is channeled through swirlerassembly 14 after exiting IFC 12. After exiting annular premix passage16, the fuel/air mixture enters combustor reaction zone 26 wherein themixture is ignited. It should be understood that there are a pluralityof nozzle assemblies 10 in an annular array about a turbine housing (notshown). It should also be appreciated that the term “fluid” as usedherein includes any medium or material that flows, including, but notlimited to, gas and air.

Premix nozzle assembly 10 operates as a “soft fuel nozzle.” As usedherein the term “soft fuel nozzle” refers to combustion pressure wavesthat may feed back into fuel passages 76 and 78 (shown in FIG. 1). Thus,in the exemplary embodiment, a fuel nozzle pressure ratio, defined asthe fuel supply pressure divided by the combustor pressure, is less thanabout 1.07 to 1.10. Above such a pressure ratio range, nozzle assembly10 is called a “hard fuel nozzle” and damaging dynamics may be produced.Another type of damaging dynamics may be produced when the fuel nozzlepressure ratio is below an acceptable minimum fuel nozzle pressureratio. Such damaging dynamics are capable of quickly ruining a turbineengine. Thus, in the exemplary embodiment, a safe fuel nozzle pressureratio range is between the minimum fuel pressure ratio and 1.07 to 1.10.It should be understood that altering the non-design gas fueltemperature may influence dynamics development.

FIG. 4 is an enlarged cross-sectional view of an exemplary gas fuel jet84 and a corresponding flame-holding margin 86. As non-design gas fuelis injected through primary fuel injection orifice 70 in an injectionangle that is substantially perpendicular to pressure side 56, thenon-design fuel forms fuel jet 84. As fuel jet 84 exits orifice 70, itencounters rapidly-moving, compressed fluid cross-flow 88 which forcesfuel jet 84 to flow substantially parallel to pressure side 56. Onceconfigured, fuel jet 84 engenders flame-holding margin 86 development.It should be appreciated that fuel jet 84 flows substantially parallelto pressure side 56 and is distanced from pressure side 56 by apenetration height PH. Penetration height PH represents the relative,maximum non-design gas fuel jet penetration height into compressed fluidcross-flow 88. By reducing non-design gas fuel jet penetration height PHand by reducing non-design gas fuel reactivity relative to design gasfuel reactivity, flame-holding margin 86 may be stabilized,substantially reduced, or eliminated. It should be appreciated thatnon-design gas fuel may also be projected onto non-vane 44 surfaces suchas, but not limited to, an outer band inner surface 47 (shown in FIG. 2)and outer surface 52 (shown in FIG. 2), which may also cause flameholding, flashback, or both. If the momentum of fuel jet 84 is notwithin an acceptable range, a flow disturbance (not shown) may developthat causes a separation in the downstream swirler assembly 14.

FIG. 5 is a schematic diagram showing an exemplary operating window 90for non-design gas fuels in premix nozzle assembly 10. Morespecifically, operating window 90 is shown as a function of penetrationheight PH, temperature 92, and fuel nozzle pressure ratio range 94. Inthe exemplary embodiment, operating window 90 defines a regime specificto the non-design gas fuel used to facilitate preventing negativeeffects of flame-holding.

Penetration height PH is proportional to ((ρ_(fuel)×V²_(fuel))/(ρ_(air)×V² _(air)))^(1/2), where ρ_(fuel) is the density ofthe non-design gas fuel, V_(fuel) is the velocity of the non-design gasfuel, ρ_(air) is the density of compressed fluid cross-flow 88 (shown inFIG. 4), and V_(air) is the mean velocity of compressed fluid cross-flow88. Additionally, the mass flow rate of a gas fuel is given by ρ×A×V,where ρ is the density of the gas fuel, A is the effectivecross-sectional area of fuel injection orifice 70 or 72 (shown in FIG.3), and V is the velocity of the gas fuel. By manipulating theparameters (ρ_(fuel), V_(fuel), ρ_(air), V_(air)) that determinepenetration height PH, and the parameters (ρ, A, V) that determine themass flow rate, a plurality of different operating windows 90 may begenerated for each non-design gas fuel. The fuel nozzle pressure ratio,defined as the fuel supply pressure divided by the combustor pressure,is another parameter that facilitates determining or generatingoperating window 90. The fuel nozzle pressure ratio may be adjusted bymanipulating the gas fuel supply pressure which also allows manipulatingor redefining fuel nozzle pressure ratio range 94; however, it should beappreciated that heating of the non-design gas fuel may be required.

Operating window 90 may also be altered by changing the density ofnon-design gas fuel by manipulating the non-design gas fuel temperature92. By cooling the non-design gas fuel, more non-design gas fuel is ableto flow through nozzle assembly 10 while remaining within fuel nozzlepressure ratio (FNPR) range 94 which is defined by the area enclosed bylines 102, 104, 106 and 108. Likewise, changing the density ofnon-design gas fuel by increasing its temperature 92, causes lessnon-design gas fuel to flow through nozzle assembly 10 while remainingwithin fuel nozzle pressure ratio (FNPR) range 94. It should beunderstood that increasing the non-design gas fuel temperature 92, notonly decreases the fuel density, but also decreases the non-design gasfuel velocity. Decreasing the non-design gas fuel velocity also causes arelated gas fuel pressure drop. In the exemplary embodiment, it isdesirable to provide a cooler, non-design fuel that remains within fuelnozzle pressure ratio range 94, to satisfy combustion dynamicrequirements while still providing enough fuel for desired turbineengine output; however heating the non-design fuel may be required.Changing the fuel temperature enables the non-design fuel to operate atthe desired range of engine output. In addition, changing the fueltemperature can also facilitate increasing the range of power outputallowable for the design fuel. For example, cooling the fuel temperaturecan reduce fuel reactivity which facilitates reducing flame holding andauto-ignition propensity, thus providing additional operating margin.

A flame-holding margin boundary 96 distinguishes between a flame-holdingregion 98 above boundary 96, and a non-flame-holding region 100 belowboundary 96. It should be appreciated that flame-holding margin boundary96 is fuel specific and depends on the reactivity of the non-design gasfuel used, and as such is different for every type of non-design gasfuel. Flame-holding region 98 indicates that there is a flame-holdingmargin 86 and non-flame-holding region 100 indicates that there is noflame-holding margin 86. In the exemplary embodiment, thermaltemperature lines of a non-design gas fuel including fifty percenthydrogen (H2) and fifty percent carbon monoxide (CO), at two differenttemperatures, are also illustrated. More specifically, a first thermaltemperature line 102 represents a non-design gas fuel having atemperature 92 of about 300⁰ F. A second thermal temperature line 104represents the same non-design gas fuel at a temperature 92 of about 80⁰F. Moreover, fuel nozzle pressure ratio range 94 is defined by a lowerpressure ratio limit 106 and an upper pressure ratio limit 108.

The area below boundary 96 that is above thermal temperature line 102and is also within fuel pressure ratio range 94, defines an operatingwindow 90 corresponding to a turbine engine using the given non-designgas at a temperature 92 of about 300⁰ F. Likewise, the area belowboundary 96, that is between boundary 96 and thermal temperature line104, and that is also within fuel pressure ratio range 94, defines anoperating window 90 for a turbine engine using the given non-design gasat a temperature 92 of about 80⁰ F. As can be seen by comparing thermaltemperature lines 102 and 104, using lower temperature non-design gasfacilitates decreasing jet penetration height PH by about a third. Thus,it can be seen that cooling the temperature 92 of non-design gas fuelsfacilitates reducing penetration height PH and substantially reduces oreliminates flame-holding margin 86. Because cooling non-design gas fuelsreduces the fuel momentum ratio and produces a cooler jet with a lowerjet penetration height PH, flame-holding margin 86 is facilitated to bedecreased.

It should be understood that for fuel orifices having fixed geometries,such as fuel injection orifices 70 and 72, pressure is proportional to(V² _(fuel)×ρ_(fuel))/2, where V_(fuel) is the velocity of thenon-design gas fuel and ρ_(fuel) is the non-design gas fuel density.Thus, a fuel having a high volumetric flow requirement, such as a lowModified Wobbe Index (MWI) non-design gas fuel, may be sufficientlycooled to generate the same power output as the design gas, such thatturbine engines with design gas fuel nozzles may operate as “soft fuelnozzles” using low MWI non-design gas fuels. It should be appreciatedthat the Wobbe Index is usually the heat content (LHV) divided by thesquare root of the molecular weight ratio. The Modified Wobbe Index(MWI) assumes that the gases are at different temperatures and the unitswould have a square root of absolute temperature. As used herein, a lowMWI non-design gas fuel ranges from about 15 to 70, which is differentthan an MWI design gas. Methane-based natural gas fuels generally havean MWI of about 39 to 55 depending on fuel temperature and composition.Furthermore, it should be appreciated that the increased load of aturbine engine is satisfied by increasing the flame temperature. Tosatisfy increased turbine engine loading, a temperature 92 range for anon-design gas fuel may be decreased for one or more fuels withdifferent MWI, due to the fuel pressure ratio.

It should be appreciated that in the exemplary embodiment non-design gasfuel is provided to turbine engines through underground pipelines, thusensuring a relatively constant, cool, non-design gas fuel supply.However, in other embodiments, any means may be employed to coolnon-design gas fuel such that nozzle assembly 10 functions as describedherein. Moreover, it should be appreciated that although the exemplaryembodiment is described as a cooled, non-design gas fuel, in otherembodiments, various compositions of non-design gas fuels may be used,and depending on the composition of non-design gas used, such fuels maybe heated or cooled such that turbine engines with design gas fuelnozzles operate as “soft fuel nozzles.” When cooling the non-design gasfuel, proper consideration of the dew point for condensation andJoule-Thompson effect in valves should be considered which may limit thelower temperature or require reduction in concentration of some fuelconstituents for cooling or both. It should be appreciated that coolingnon-design gas fuel reduces the fuel's reactivity and potentiallydecreases flame holding an auto-ignition.

It should be understood that some non-design gas fuels have a highervolumetric flow rate requiring larger fuel injection orifices than ispermitted for existing design gas fuel operation. Consequently,operating turbines with non-design gas fuels having a higher MWI mayrequire heating during premixing operations in nozzle assembly 10 withone premixed fuel passage, 76 or 78 (shown in FIG. 1), per fuel nozzleassembly 10, to facilitate maintaining the minimum allowable fuel nozzlepressure ratio and not to “flame-hold” with fuels having lower MWIindexes. As used herein, a high MWI non-design gas fuel has a higher MWIthan design gas.

It should be appreciated that controlling flame-holding margin 86facilitates using non-design fuels that facilitate reducing nitrousoxide (NOx) emissions. More specifically, because controllingflame-holding margin 86 allows using a wider variety of non-design gasfuels, non-design gas fuels that inherently or more effectively reduceNOx and CO emissions when burned, may be used for combustor designs. Forexample, if a non-design gas fuel produces one part per million NOx whenburned and the design gas fuel produces five parts per million NOx whenburned, it may be better to operate a turbine engine using non-designgas fuel to reduce NOx emissions. Moreover, it should be appreciatedthat the design gas fuel may be heated to improve penetration, improvefuel mixing to decrease NOx emissions and reduce damaging dynamics.

It is desirable to increase the fuel flexibility of turbine engines byoperating turbine engines with less expensive, and morereadily-available alternative non-design gas fuels, rather than designgas fuels. Such alternative non-design gas fuels include, but are notlimited to, liquefied naural gas (LGN), syngas and process gas. Usingalternative fuels requires providing sufficient flame-holding margin inpremixed fuel nozzles. It should be appreciated that controlling jetpenetration height produces acceptable flame-holding margin foroperation on a single fuel passage and extends flame-holding margins.

FIG. 6 is a schematic diagram showing an alternative exemplary operatingwindow 110 for non-design gas fuel in diffusion nozzle assemblies (notshown). Diffusion nozzle assemblies mix non-design gas fuel andcompressed fluid, and ignite the combination where it is mixed.Operating window 110 is shown as a function of fuel nozzle pressureratio 112 and fuel nozzle flame temperature 114. It should be understoodthat operating window 110 defines a regime specific to the non-designgas fuel used to facilitate preventing the negative effects offlame-holding.

Thermal temperature lines of a non-design gas fuel including fiftypercent hydrogen (H2) and fifty percent carbon monoxide (CO), at twodifferent temperatures, are also illustrated. More specifically, a firstthermal temperature line 116 represents a non-design gas fuel having atemperature of about 300⁰ F. A second thermal temperature line 118represents the same non-design gas fuel at a temperature of about 80⁰ F.In the exemplary embodiment, operating window 110 indicates the minimumand maximum pressure ratio over which combustion dynamics are acceptablefor diffusion nozzle assemblies. Increasing the fuel temperaturedecreases the fuel density such that fuel jet 84 velocity increases forthe same non-design gas fuel flow to deliver the same mass of fuel to acombustion chamber. It should be understood that operating withinoperating window 110 provides adequate turbine engine power and does notengender development of damaging dynamics.

In each embodiment, the above-described methods of controllingflame-holding margins facilitate increasing the range of fuelcompositions that can be safely used in existing turbine engines with areduced-cost, single-premixed circuit. Moreover, existing turbineengines may operate with different fuels without requiring installationof new fuel nozzles. Furthermore, non-design gas fuel heating andcooling circuits could be integrated into systems for minimizing cyclelosses. Such circuits may include heating non-design gas fuel in anexhaust stack and cooling non-design gas fuel with make up water. Morespecifically, in each embodiment, changing the fuel temperature andoperating within a fuel pressure ratio range, stabilizes, substantiallyreduces or eliminates flame-holding margins. As a result, fuelflexibility of existing turbine engines and operation of existingturbine engines with a single fuel circuit are provided. Accordingly,turbine performance and component useful life are each facilitated to beenhanced in a cost-effective and reliable manner.

Exemplary embodiments of methods for controlling flame-holding marginsare described above in detail. The methods are not limited to use withthe specific turbine embodiments described herein, but rather, themethods can be utilized independently and separately from othercomponents described herein. For example, the methods may be used withany utility, industrial or mechanical drive turbine. Moreover, theinvention is not limited to the embodiments of the method describedabove in detail. Rather, other variations of the method may be utilizedwithin the spirit and scope of the claims.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1. A method to facilitate operating within flame-holding margins in aturbine engine, said method comprising: coupling at least one turbinenozzle segment within the turbine engine, wherein the at least oneturbine nozzle segment includes at least one vane extending between aninner band and an outer band; positioning at least one fuel injectionorifice in a surface of the at least one vane; channeling a fuel throughthe at least one fuel injection orifice into a compressed fluid flow toestablish a jet penetration height; and defining an operating window byadjusting an operating parameter of the fuel to reduce the jetpenetration height and to facilitate increasing the flame-holdingmargins.
 2. A method in accordance with claim 1 further comprising:sizing the at least one fuel injection orifice to operate using a designfuel; and channeling a non-design fuel through the at least one fuelinjection orifice.
 3. A method in accordance with claim 1 whereindefining an operating window by adjusting a parameter of the fuelfurther comprises adjusting a density of the fuel by changing atemperature of the fuel.
 4. A method in accordance with claim 3 furthercomprising changing the temperature of the fuel to facilitate altering amomentum ratio of the fuel.
 5. A method in accordance with claim 1wherein defining an operating window by adjusting a parameter of thefuel further comprises adjusting a fuel nozzle pressure ratio range bychanging a temperature of the fuel.
 6. A method in accordance with claim1 wherein channeling a fuel through the at least one fuel injectionorifice further comprises channeling a non-design fuel having a modifiedwobbe index that is lower than a modified wobbe index of the design fuelthrough the at least one fuel injection orifice.
 7. A method inaccordance with claim 1 wherein channeling a fuel through the at leastone fuel injection orifice further comprises: channeling a non-designfuel through the at least one fuel injection orifice, wherein thenon-design fuel has a higher modified wobbe index (MWI) than an MWI ofthe design fuel; and at least one of heating and cooling the non-designfuel.
 8. A method in accordance with claim 1 wherein channeling a fuelthrough the at least one fuel injection orifice further compriseschanneling a non-design fuel through the at least one fuel injectionorifice, wherein the non-design fuel is at least one of liquefiednatural gas, syngas and process gas.
 9. A system to facilitate operatingwithin flame-holding margins in a turbine engine, said systemcomprising: at least one turbine nozzle segment coupled within theturbine engine, said at least one turbine nozzle segment comprises atleast one vane extending between an inner band and an outer band; adesign fuel from a fuel source; at least one fuel injection orificedefined in a surface of the at least one vane, said at least one fuelinjection orifice designed to optimize turbine performance using saiddesign fuel; a non-design fuel channeled through the at least one fuelinjection orifice into a compressed fluid flow to establish a jetpenetration height; and an operating window to facilitate reducing thejet penetration height and to facilitate increasing the flame-holdingmargins.
 10. A system in accordance with claim 9 wherein said operatingwindow is established by adjusting an operating parameter of saidnon-design fuel.
 11. A system in accordance with claim 9 wherein saidoperating window is defined by adjusting a density of said non-designfuel by changing a temperature of said non-design fuel.
 12. A system inaccordance with claim 11 wherein the temperature is reduced to adjust anon-design fuel momentum ratio.
 13. A system in accordance with claim 9wherein said operating window is defined by adjusting a fuel nozzlepressure ratio range by changing a pressure of said non-design fuel. 14.A system in accordance with claim 9 wherein said non-design fuel has amodified wobbe index lower than a modified wobbe index of the designfuel.
 15. A method in accordance with claim 9 wherein said non-designfuel is heated and has a higher modified wobbe index than the designfuel.
 16. A method in accordance with claim 9 wherein said non-designfuel is at least one of liquefied natural gas, syngas and process gas.17. A turbine engine comprising a nozzle assembly comprising an innerband, an outer band, and at least one vane extending between said innerband and said outer band, said vane comprising a plurality of fuelinjection orifices designed to optimize performance using a design fueland configured to channel a non-design fuel therefrom to facilitatecontrolling flame-holding margins.
 18. A turbine engine in accordancewith claim 17 wherein said inner band comprises at least one fuel supplypassage configured to supply said non-design fuel to at least one ofsaid plurality of fuel injection orifices.
 19. A turbine engine inaccordance with claim 17 wherein said non-design fuel is at least one ofliquefied naural gas, syngas and process gas.
 20. A turbine engine inaccordance with claim 17 wherein said non-design fuel is cooled toreduce a jet penetration height and a flame-holding region.